The present invention relates to drill bit assemblies used in the underground exploration of petroleum products. More specifically, the invention relates to a sliding seal ring preferably made of an elastic metallic strip material which seats in the drill bit assembly between the drill bit body and the rotary cutter with an initial axial tension.
A seal ring of this type is illustrated in U.S. Pat. No. 3,361,494. This seal ring is conically shaped in the nature of a plate spring. By reason of this shape it has only a small amount of elastic flexibility in an axial direction and none at all in a radial direction and this presents certain disadvantages and drawbacks when used in drill bit applications of the type to which the present invention relates. For example, in order to incorporate this known seal ring in a drill bit assembly with a certain predetermined initial tension which is necessary to provide a seal between the rotary cutter and the drill bit body, the sliding surfaces of the rotary cutter and drill bit body must be fabricated with very close tolerances since they determine the position of the seal ring and accordingly, its effectiveness to provide the necessary seal. Of course, maintaining these tolerances adds to the expense in the production of the drill bit assembly. Furthermore, the normal amount of wear which occurs in the assembly over a period of time produces a predetermined amount of radial and axial play in the bearings of the rotary cutter. As a result of this play, the known seal ring with its limited flexibility no longer elastically bridges the surfaces of the rotary cutter and drill bit body and thus loses its effective sealing function. The consequent penetration of drilling mud accelerates wear in the bearings caused by rock particles and the like which are no longer blocked out by the seal ring. Thus the entire assembly has a relatively brief service life or operating period.
Furthermore, as the bearing wear increases, the action of the rotary cutter on the drill bit body is no longer pure rotational but may be described as a tumbling motion which in the case of the conventional seal ring is at best only partly elastically absorbed. Additionally this tumbling motion deforms the conventional seal ring and damages it after a short life span by reason of overstressing due to the tumbling motion of the rotary cutter.